In the application of industrial robots, cases arise in which positioning of an object by repetitive positioning operations in accordance with an instruction position may be unsatisfactory. This can be due to various reasons, e.g. because a sufficiently high degree of positioning accuracy cannot be obtained, because the relative positions of the robot and the object may vary, because the size of the object may vary, or because the execution of such positioning or apparatus required to perform the positioning results in excessively high cost. There is therefore a strong requirement for sensing the position of the object, and performing correction of the robot position with respect to the instruction position based on the results of this sensing.
Among the methods which have been proposed to achieve this are for example the use of an optical recognition apparatus or use of an ultrasonic wave detection apparatus for sensing the object position, with the data representing the results of this sensing being transferred to the robot and the robot then executing positioning correction on the basis of this data. However such methods present the disadvantage of requiring the use of a dedicated optical recognition apparatus, or ultrasonic wave detection apparatus for each robot. This is undesirable from the aspect of cost. In addition, such methods are disadvantageous because of problems which they present with regard to position sensing in three dimensions.